Multiple grid electrode



May 22, 1928.

J. W. GREENBOWE MULTIPLE GRID ELECTRODE Filed Oct. 17, 1924 II p! FIG]INVENTOR J. WALTER GREENBOWE.

ATTORNEY Patented May "22, 1928.

UNITED STATES 1,610,503 PATENT OFFICE.

JAMES GREENIBOWE, O1 BAYONNE, NEW JERSEY ASSIGNOR TO WESTING- HOUSE LAMPCOMPANY, A CORPORATION .01 PENNSYLVANIA.

MULTIPLE emn'nnncrnonn.

Application filed October 17, 1924. Serial No. 744,155.

This invention relates to electron discharge devices such as radiotubesused as detectors or as audio or radio frequency amplifiers andmore particularly to radio tubes employing more than cine gridelectrode.

An object of the invention is to simplify the construction of a doubleor multiple electrode.

.Another object of the invention is to provide an electrode having aplurality of integral tubular cathode receiving portions.

A further object of the invention is to provide a grid element which maybe accurately and quickly produced.

Other objects and advantages of the invention will be apparent as thedescription proceeds.

When roducing a radio tube, it is desirable to o tain a maximum mutualconductance, with a given amplification constant as well as to reducethe plate resistance and to provide as large an electron emittingsurface as is possible.

It has been found that by multiplying certain of the elements within atube, conditions may be provided to give the results desired. 7

In tubes in which a relatively long cathode is required, it is obviouslynecessary to make the plate electrode and consequently the grid of suchproper shape: as

i to be in close proximity to the entire length of the filament.

Owing .to the necessity of employing relatively fine wire as thecathode,it has been found impractical to make the cathode of comparatively greatlength since the cathode has a tendency to sag by reason of, the weightof the wire. This disadvantage is, however, greatly reduced when severalrelativel short cathodes or filaments are used. It tli erefore becomesnecessary to provide other elements such as the plate and grid of suchconstruction as to be quickly and accurately made for use with the shortfilaments.

The present invention aims to provide a simplified form of grid whichmay be quick- I made at low cost and which will answer the requirementsof grids as heretofore produced for radio tubes employing a singlefilament.

The present invention contemplates the formation of a multiple grid froma single on sheet of stamped metal and is an application, generally, ofthe idea embodied in my copendmg application Serial N 0. 694,552. filedFebruary 23, 1924 and assigned to the same assignee as is the presentapplication. 00

The present embodiment of the invention includes the formation from asingle sheet of metal, a plurality of tubular shaped grids forsurrounding electrodes.

The invention will be more fully underno stood by reference to theaccompanying drawing, in which Fig. 1 is .a perspective view ofthermonic. tube partly broken away and showing the elements therein,some of which are also single piece of perforated metal;

Fig. 7 is an elevational view of Fig. 6;

- Fig. 6 is a plan View of a,- double grid having tubular portionsformed from a Fig. 8 is a plan view of a double grid,

formed from oppositely bentportions of a' sheet of perforated metal, andi Fig. 9 is an elevational View of the grid shown in Fig. 8.

As shown, the various elements of a discharge tube may include an anodeor plate 15, a grid 16 and one or more cathodes or filaments 17. Theseelements are suitably mounted Within an evacuated envelope 18 includinga pedestal 19 terminating in a press 21 having embedded therein, theseveral various support members upon which the electrodes are mounted,the plate being carried on supports 22 and 23, the latter having a conThe plate may be provided with lips 25 at its .upper and lower edgeswhich may be bent to grip the supports 22 and 23 and a welding operationmay be performed for more securely joining the supports to them;

lips.

The grid 16 may be mounted on a rigid.- support member 26 and securedthereto in uctor 24 connected thereto. 10

a .manner hereinafter more fully described. A conductor 30'may beprovided and connected to the support 26.

Filaments 17 may have their lower ends fastened to supports 27 and 28towhich conductors 29 and 31, respectively, are attached and the ,upperends of the filaments may be secured to a cross bar 32-which in turn issupportedby a comparatively rigid memlo ber 33 having'its lower endsecured in the press.

' A grid for enclosing a plurality of filaments is, accordingto thepresent invention, produced by piercing a plate 34 (see Fig. 2)

v of suitable material with a plurality of apertures 35 to provide crossbars 36 and 37. The cross bars will initially be positioned in a commonplane before the plate 34 is formed to provide av grid.

When the forming operation hasbeen accomplished, each cross bar will bebent into an opposite sinuous form. For example, as shown'more clearlyin Fig. 3, the cross bar 36 will be formed with a'bend 38 at .one. sideof a common plane and a bend 39 atthe opposite side of the plane. Thecross bar 37 will have a bend 41 upon one side of the plane opposite tothe bend 38 and a bend42 on one side of the plane opposite" to that-towhichfthe bend 39- is disposed.

Each alternate bar having an opposite sinuous shape "provides tubulargrid passages 43 in which the filaments 17 may Zbe pos1 tioned. Itwill,'of course, be understood v that when desirable, a grid may, in theabove manner, beyformed wlth .more thantwo grid passages-by providingcross bars 36 and 37 of suitable length to allow for a pluralityof-bends in alternate bars and thus a series of grid passages-may,beforme'd.

Furthermore, in order'to expedite manufacture, it maybe desirable toprovide grids by having a plurality of sets of slots 35 separated byconnector strips 44. A continuous 45 strip 34-may, therefore, be punchedfrom a sheet and as each set of cross bars is formed, the same may besevered from the strip and bent into grids.

Although a grid made in accordance with 60 the present invention maybesupported in various ways, one mode of attachment to a; support'consists inproviding relatively broad upper and lower cross pieces 45and 46 to which the support member 26 may be welded or otherwisesecured.

1 As shown in Figs 4 and 5, a modified form of the grid is shown havinga plurality of grid passages 43. This is accomplished by punching aplate 47:with two sets of elongated apertures 48 and 49 in spacedrelation to provide cross bars 51 and 52, apertures 48 resulting incrossbars 51 and 52 therebetween, and apertures 49 providing cross bars 53and 54 therebetween. Grid passages 43 are provided by bending the Asshown in Figs. 6 and 7, double grid passages 43 may be provided bypiercing a plate to provide two sets of apertures 58 and 59 to givecross bars 61 and 62. Each series of cross bars may be bent tosubstantially circular form and the plate may be bent to provide a loop63 in which a support mem-.

ber 64 may be welded or otherwise secured.

'Figs. 8 and 9 show a grid having double grid passages 43, the grid alsobeing formed from a plate having two sets of slots or apertures 65 and66 and cross bars 67 and 68. The cross. bars may be bent to provide anS-shaped grid in transverse cross section and one edge of the'plate fromwhich the grid is't'ormed may be bent to provide a tubular aperture 69to receive a support 71.

The present invention makes it possible to provide a double or multiplegrid or plate having all of its members integral and at the same timeproviding enc'losuresfor the filament.

Inasmuchas it has been found advanta-- geoussto bring a plateand-gridinto close relation, the. advantage of the present form of gridwill be evident. Plates having contours to correspond to the presentforms 'of 'grid may be quickly and conveniently produced.

It will further be appreciated that a relatively few operations arenecessary to menu facturethespresent form of grid and that alloperations may be quickly and. automatically performed. The desirabilityof accu- Inn rately positioning the cross-bars of a grid is'wellrecognized, particularly is it desirable in the manufacture of a doublegrid to be able to positively and precisely position the many crosspieces which constitutethe grid.

When manufacturing'a grid adapted to surround a filament, it is nosimple matter to properly and dependably construct a grid. The operationof winding a wire about support members to form a grid is not only morecostly inasmuch as the wire must be automatically secured to the sup--ports,'but it is not always possible todepend upon the accurateposition of one turn of wire with relation to another and the spacingbetween "the wires is trequently not uniform.

With the present grid, however, it is obvious that by bending the crosspieces to their proper position, an accuracy and precision in thedisposition of the members is possible due to themechanical elementssuch as the dies which perform the bending oper ation. By reason of thisconstruction, agrid is produced which when used ina tube, will giveuniform characteristics answering the requirements of standard practice.A grid or plate'produced in accordance with the present invention is ofa seamless character and provides a plurality .of endless encirclingmembers.

The present construction of grid makes it possible to produce the sameat a relatively high. rate of speed and with a single operation of apunch press.

Furthermore, the rigid cross bars will be accurately positioned withrespect to each other and will resist displacement duringthe essentialhandling during assembly, to a greater extent than will grids asheretofore constructed of wire wound on and secured to supports.

'The accurate disposition of the cross bars combined wtih the rapiditywith which the grid can be produced makes the present invention animportant advance step in radio tube manufacture.

It will be understood that plates as well as grids may be madeinaccordance with the present invention and that the relative positions ofthe cross bars on the grid and plate when mounted in a thermionic tubemay be easily positioned in the most effecthe manner.

It is to be understood that although a preferred embodiment of theinvention is shown, such modifications as above set forth device formedfrom a sheet of material and comprising support members disposed in acommon plane and connected by a lurality of cross-members punched fromsaid sheet, said cross-members being bent to dispose portions thereof atopposite sides of said metal, said control electrode having a pair ofsuppm't-membcrs connected by cross-bars punched from said sheet disposedin spaced relation and bent to extend from opposite sides of said sheetto provide a plurality of enclosures for said cathodes and an anodehaving the wall thereof shaped for disposition in synnnetric spacedrelation about said grid.

4. An electron discharge device comprising an anode, a plurality ofcathodes,-and a control electrode formed from a sheet of metal, saidcontrol electrode having a pair of support members disposed in a commonplane and connected by a plurality of cross bars punched from said sheetand disposed in spaced relation, said cross-bars being of reversecurvature form, the curvature of each alternate crossbar being in anoppo site direction to provide a plurality of enclosures and an anode having the wall thereof formed for disposition in symmetric spacedrelation to said grid. 5. The method of forming a control element for anelectron discharge device which comprises punching a plurality ofapertures in a sheet of material to provide spaced connector members andbending said members to bring a portion of each member on an op positeside of the normal plane of the members to provide a plurality ofenclosures.

In testimony whereof, I have hereunto subscribed my name this 15th dayof October 1924.

JAMES WALTER GREENBOWE.

